Quarterwave stacks and quasi-sinusoidal rugate structures are unified by the introduction of the power-sine rugate structures. Changing one parameter modifies the optical admittance profile continuously from quarterwave stack to rugate structure. The fact that power sine rugates have adjustable high order harmonics can be used for the design of non-polarizing coatings.
Recent progress in ion beam polishing has successfully led to the production of smooth diamond films. By means of an oxygen ion beam, a 5 cm diameter, 1 micrometers rough film grown by microwave plasma chemical vapor deposition on silicon has been polished. The polished film root-mean-square and peak-to-valley roughness values averaged over 15 points are respectively 5.5 nm and 55.4 nm. Scattering has been decreased to the point where the polished film is transparent at wavelengths above the silicon absorption edge and shows interference fringes. This suggests that diamond films polished by this process can be used in optical applications. This paper describes the polishing technique and presents the results obtained by surface profilometry of the polished sample. The main advantages of ion beam polishing over other existing methods lie in the fact that it is noncontact and low-temperature technique.
In our program for ion beam polishing of microwave-assisted chemical vapor deposited diamond films using a planarizing layer we have sought to develop the technique by polishing AT-cut quartz disks used in rate monitors as an intermediate objective. Using an argon ion beam and spin-coated photoresist as the planarizing layer we successfully reduced the peak-to-valley (p-v) surface roughness from 5 pm to 0. 2 pm. In the case of diamond films whose etch rate is minute under argon bombardment reactive oxygen ions constituted the beam. The planarizing overcoat designed so that its etch rate would match that of the diamond film was a mixture of photoresist and titanium-silica. With this combination we reduced the diamond films'' surface roughness from 6 jim and 1 pm to 217 nm and 35nm p-v and mis respectively. This successful diamond film polishing opens the field of infrared optics to these materials. 1.
The refractive index dependence on temperature and electric field can cause drastic modifications on
the optical properties of optical filters. A simulation has been developed which handles electric field and
temperature dependent refractive indices in multilayer stacks. In this paper we have restricted ourselves to
an electric field dependence and results obtained for single line rugate filters designed by the modified
Fourier transform technique, are presented.
Silicon nitride films were synthesized in a Balzers BAP 800 coating plant by an
plasma enhanced evaporation process. Transparent, stoichiometric films free of
hydrogen, oxygen, argon, and heavy metals were obtained. The optical properties,
the chemical composition, the microhardness, the structure, and the morphology of
the films were investigated.
This paper examines the effects of angle of incidence changes on the optical properties of rugate filters. Like quarterwave dielectric stacks rugate filters are sensitive to tilting: their reflectance bands shift to shorter wavelengths and their optical properties become polarization dependent. Tilting a quarterwave stack also produces a drop in the transmittance in the middle of the passband this drop is called the halfwave hole. In single line rugate filters a similar behavior is observed and multiple holes corresponding to harmonics of the main reflectance bands appear in the pass band. In multiline rugate filters the situation is even more complicated: the large number of harmonics already present is increased by supplementary peaks produced by beating between each family of harmonics. All these reflecting bands are located on the short wavelengths side of the main bands and they can be such that most of the light is reflected. Some possible solutions are suggested involving the use of aperiodic structures. 1.